Inheritance of partial resistance to sclerotinia stem rot in soybean

Inheritance of partial resistance to sclerotinia stem rot in soybean

2000

A:PS

Little is known about the inheritance of partial resistance in soyabean (Glycine max) to sclerotinia stem rot, caused by the fungal pathogen Sclerotinia sclerotiorum. This information would be useful to soyabean breeders who are developing cultivars withresistance to sclerotinia stem rot. Our objectives were to study the inheritance of partial resistance to sclerotinia stem rot and to present the initial results from mapping quantitative trait loci (QTL) that confer this resistance. The research was conducted by testing 152 F3-derived lines from a cross between a partially resistant cultivar, Novartis Seeds S19-90 (formerly Northrup King), and a susceptible cultivar, Williams 82, for resistance to sclerotinia stem rot and agronomic traits at two Michigan locations in each of 2 yr. These lines were also evaluated for 123 genetic markers to map resistance genes. The resistance of the lines, measured using a disease severity index (DSI), was normally distributed across environments. Significant (P <0.05) genotypic variation, genotype X location, and genotype X year interactions were observed for DSI. The broad-sense heritability estimate for DSI across both locations and years was 0.59. More severe disease was significantly correlated with greater lodging, later date of maturity, later R1 date, and greater plant height. Three QTL, explaining 10, 9 and 8% of the variability for DSI across environments, were mapped with genetic markers. Two of these QTL were also significantly associated with disease escape mechanisms such as plant height, lodging and date of flowering. The other QTL was not significantly associated with escape mechanisms and may map one or more genes involved in physiological resistance to the disease.

v.40(1):55-61, CROP SCIENCE

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